A steam turbine plant is mainly provided with a high-pressure steam turbine in which main steam performs work; an intermediate-pressure steam turbine in which reheated steam performs work; and a low-pressure steam turbine in which steam discharged from the intermediate-pressure steam turbine performs work. Among these steam turbines, the low-pressure steam turbine is coupled to a condenser, and the steam discharged from the low-pressure steam turbine is condensed in the condenser so as to generate condensate.
An inner casing of the low-pressure steam turbine is provided with a plurality of nozzle diaphragms. A labyrinth packing is provided to an inner peripheral end of each nozzle diaphragm to prevent the steam from passing through regions between the nozzle diaphragms and a turbine rotor. Accordingly, it is possible to reduce detriment attributable to steam leakage, which leads to improvement in performance of the turbine.
The nozzle diaphragms receive a swirling force from the steam passing through turbine stages and receive a turning moment centering on a shaft center line of the turbine rotor. Accordingly, the inner casing may be displaced in a direction orthogonal to an axial direction of the turbine rotor (hereinafter referred to as an “axis-orthogonal direction”). In this case, the labyrinth packing or a part of a stationary unit comes into contact with the turbine rotor or a part of a rotary unit, which is a problem.
To solve such a problem, an outer casing of the low-pressure steam turbine is provided with a supporting member that restricts movement of the inner casing in the axis-orthogonal direction. If the low-pressure steam turbine is a lower exhaust turbine beneath which a condenser is connected, the supporting member is formed so as to extend in the axial direction (horizontal direction) of the turbine rotor from an end plate of the outer casing.
An example of the low-pressure steam turbine includes a turbine of lateral exhaust type (hereinafter referred to as an “lateral exhaust turbine”). A condenser is connected to a side of this lateral exhaust turbine. In a case where the supporting member extending in the horizontal direction from the end plate is used in this lateral exhaust turbine, there is a problem that the supporting member obstructs a steam flow. In this case, a pressure loss of the steam increases, which may degrade performance of the turbine.